A retardation film used in a liquid crystal display device or the like can be produced by a method such that an orientation layer (orientation film) formed on a substrate is irradiated with polarized ultraviolet light to perform an orientation treatment thereon, thus obtaining an optical orientation film; and liquid crystal is applied onto the orientation layer subjected to the orientation treatment of the optical orientation film and oriented, thus forming a retardation layer.
As such a method of orientation treatment of the orientation layer, there has been reported several methods using a photodimerization reaction, photolysis reaction or photoisomerization reaction, such as a method of controlling the direction of cross-linking formation in a polyvinyl cinnamate orientation layer by irradiation with polarized ultraviolet light (for example, see Non Patent Literature 1) and a method of providing anisotropy to the decomposition of a polyimide orientation layer by irradiation with ultraviolet light (for example, see Non Patent Literature 2).
In recent years, development of techniques for displaying and viewing pictures and images three-dimensionally, is encouraged.
One of the methods for displaying three-dimensional images is a method using polarized glasses (for example, see Patent Literature 1).
An example of the polarized glasses method using a liquid crystal display device is as follows: as shown in FIG. 11, an image (lights) for right eye for 3D viewing is emitted from an even number of lines of panel (display surface) 250 of the liquid crystal display device, while an image (lights) for left eye for 3D viewing is emitted from an odd number of lines. Among the lights for 3D viewing, only the linearly polarized lights which are in the same longitudinal direction as that of polarization axis (transmission axis) 270 of first polarizing plate 260 pass through first polarizing plate 260.
Then, among the linearly polarized lights which passed through the polarizing plate, the light for right eye emitted from the even number of lines of the display surface, which show the image for right eye for 3D viewing, passes through first λ/4 plate 290 in which slow axis 280 is inclined at 45° to polarization axis 270 of first polarizing plate 260. As a result, the light for right eye is converted into circularly-polarized light (elliptically-polarized light) 300. Similarly, among the linearly polarized lights which passed through the plate, the light for left eye emitted from the odd number of lines of the display surface, which show the image for left eye for 3D viewing, passes through first λ/4 plate 291 in which slow axis 281 is inclined at −45° to polarization axis 270 of first polarizing plate 260. As a result, the light for left eye is converted into circularly-polarized light (elliptically-polarized light) 301. At this stage, depending on the slope (45° or −45°) of the slow axis of each first λ/4 plate, each linearly polarized light is converted into right-handed or left-handed circularly-polarized light (elliptically-polarized light).
Next, second λ/4 plate 320 in which slow axis 310 is perpendicular to slow axis 280 of first λ/4 plate 290, transmits circularly-polarized light (elliptically-polarized light) 300 to convert the light into linearly polarized light in a longitudinal polarization direction. Similarly, circularly-polarized light (elliptically-polarized light) 301 is converted into linearly polarized light in a longitudinal polarization direction through second λ/4 plate 321.
At this stage, depending on the combination of the slope of the slow axis of each second λ/4 plate and the right-handed or left-handed circularly-polarized light (elliptically-polarized light), the circularly-polarized light (elliptically-polarized light) is converted into linearly polarized light in a longitudinal polarization direction or linearly polarized light in a lateral polarization direction. By controlling the slow axes of the first and second λ/4 plates, only the desired light from each of the light for right eye and that for left eye can be converted into a specific polarization direction.
Then, the images for right and left eyes converted into a specific polarization direction (longitudinal direction) through second polarizing plates 261a and 261b with polarization axis 271 in a longitudinal direction, are separately taken out. The images for right and left eyes are separated through first λ/4 plates 290 and 291, and the separated images for right and left eyes are respectively received by the right glass and left glass of polarization glasses 330, the right glass comprising a combination of second λ/4 plates 320 and second polarizing plates 261 and the left glass comprising second λ/4 plates 321 and second polarizing plates 261, thereby making 3D viewing possible.
In FIG. 11, first λ/4 plates 290 and 291 are schematically and separately shown, in each of which the slope of slow axis 280 or 281 is varied depending on the even or odd lines. In general, however, one λ/4 plate (retardation film) is needed, in which parts with different slow axes at different slopes are disposed in a pattern. As described above, a retardation film is produced by forming a retardation layer on an orientation layer (orientation film); therefore, a λ/4 plate for 3D viewing needs one orientation layer in which parts in different orientation directions are disposed in a pattern.
In the production of the orientation layer (orientation film), when the substrate is a sheet-like substrate such as a glass substrate, as shown in FIG. 12 of Patent Literature 1, a photomask is kept above an orientation film to be shielded from light, having a constant interval (or a proximity gap, hereinafter it may be simply referred to as “gap”) therebetween. After an orientation treatment is performed on the orientation film by exposing the film to polarized light radiation through a mask in a pattern, the photomask is removed therefrom. Then, the orientation film is entirely exposed to polarized ultraviolet light in a polarization direction (polarization axis) which is different from that of the pattern exposure. Thereby, an optical orientation film is produced, in which parts in different orientation directions are disposed in a pattern in the orientation layer.